I'm planning to connect 3 3560's and a 4503 together in a ring topology, with dual fiber cables connecting each switch in a port channel group.
I want to use MST for fast restoration of service in the event of a break in the physical network.
My first question - Are there any known problems with MST and port-channel interfaces? In the MST configuration document, Cisco has redundant trunks which use the "spanning-tree mst 2 port-priority 64" command to balance between them...
I'm just getting into MST and so I want to make sure that I can skip that command, as the interface should handle balancing itself.
Also, Cisco's network topology is different than mine in the example they give; is there anything inherently wrong or undoable with my approach?
It essentially looks like this.
C's represent 3560's.
Any help would be greatly appreciated.
By default, all the instances will have the same parameters, and will thus compute the same topology. So if you want different path for your two instances, you'll need to configure them differently. Apart that you need to have the same MST region configuration all over your network, the different instances are configured just like you would do in PVST mode (if you are used to PVST). Basically, you just need to replace the keyword "vlan" by "mst" in your commands;-)
Usually, the simplest way to enforce a topology is to force the root bridge at a particular location. This is done by tuning the priority of the bridge that you want to be root on this particular instance (for example: "spanning-tree mst 1 priority 8192" should be enough to make this bridge root for instance 1). Then, if you need to modify the path computed by default from this root, the simplest is generally to change the cost of the ports ("spanning-tree mst 1 cost X"). The higher the cost of a port, the less likely it will be elected root port.